The electrostatographic process, and particularly the xerographic process, is known. This process involves the formation of an electrostatic latent image on a photoreceptor, followed by development of the image with a developer, and subsequent transfer of the image to a suitable substrate. In xerography, the surface of an electrophotographic plate, drum, belt or the like (imaging member or photoreceptor) containing a photoconductive insulating layer on a conductive layer is first uniformly electrostatically charged. The imaging member is then exposed to a pattern of activating electromagnetic radiation, such as light. The radiation selectively dissipates the charge on the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image on the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic marking particles, called toner, on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the imaging member directly or indirectly (such as by a transfer or other member) to a recording medium, such as transparency or paper. The imaging process may be repeated many times with reusable imaging members.
A current trend in the printing industry is printing on stress case media, such as flexible packaging and automobile owner manuals. The flexible packaging industry includes packaging of food, pharmaceuticals, cosmetics, etc. The stress case of automobile owner manuals involves the image permanence at elevated temperatures for example, in a glove box of an automobile on a hot summer day.
Printing on stress case media can require the use of materials that are durable and that are resistant to a variety of conditions and environmental factors. Many offset printings use a heated overcoat to protect the image from abrasion. However, overcoats applied to fused and unfused images can cause degradation of image quality. Accordingly, there is a desire for a toner composition that in embodiments may not require a protective overcoat.
Furthermore, in the graphic arts industry and for a number of other entities, printing is performed on a wide array of substrates and surfaces such as on yogurt containers, foil seals for containers and other diverse packaging configurations. There can be a number of disadvantages associated with using heat fused xerographic toners in these traditionally lithographic printing applications. Many lithographic applications use an overcoat that is subsequently heated to protect images from abrasion. However, applying overcoats to fused and unfused toner can disturb the toner piles. Overcoats are usually applied with heat and this heat causes dry toners to smear and possibly undergo phase separation that can damage image quality. Accordingly, there is also a desire for a single application printing process that can avoid the need for an overcoat, and particularly can avoid a process that includes applying and heating an overcoat.
In addition, obtaining a toner formulation with low melt characteristics is desired to reduce operation costs. However, a toner with low melt characteristics often has bad offset properties. Thus, it would be desirable to provide a toner composition that is fusible with reduced heating.